UL requirements specify that to protect against power surges in telephone lines and, particularly to provide current limiting, the network must include a fusing link at any network termination, such as the outside plant (OSP) terminations located at splice points (e.g., terminal blocks), building entrances (e.g., building entrance protectors (BEPs)), and/or other premises (e.g., station protectors or network interface devices (NIDs) at homes). More specifically, for example, a network termination point where these fusing links typically have been implemented is at the terminal block that is used for connecting the telco wires of the cable that runs from the telco central office to the wires that run to subscribers' premises.
Commonly, these terminal blocks are located on a telephone pole, in a ground-based pedestal closure, within an underground handhole, or at an in-building application (e.g., on outside wall, or in building service area). For convenience, the telco wires entering the terminal block from the central office side are herein referred to as the exchange wires, distribution wires, or main wires. The wires running from the terminal to the subscriber premises (where they are terminated at an NID or station protector) are commonly referred to as service drop lines, each drop line including one or more pairs of wires (tip-ring wire pair), with each pair servicing one piece of equipment such as a telephone, a fax, or an alternative form of modem.
Fusible links are typically provided at the terminal block as a stub cable comprising individual wire segments connected in series between the terminal block terminals and each wire from the telco distribution wire. Particularly, the fusible link is implemented as the finest gauge wire in the network. Thus, if excessive energy (e.g. voltage surges) appears in the network, the fusing link will fail and the excessive energy will not travel to the telephone lines.
The fusing links provided in this manner at the terminal block are typically contained within a closure containing the terminal block. Although this closure may be implemented to provide protection from environmental damage (e.g., corrosion), terminal block modules typically have been typically implemented to provide additional environmental protection (as well as surge protection) for interconnecting the drop lines to the telco distribution wires. The fusible links, however, are not implemented in a way that provides additional environmental protection. The fusible links (including their connections) are thus susceptible to environmental effects (e.g., corrosion) and/or other damage, wear, shorting, etc. Additionally, the fusible links are not well suited for servicing (e.g., repair or replacement) or testing.